A member of link-sharing site Reddit thought he caught a scammer red-handed. He spearheaded a crusade against her, harnessing the power of one of the web's biggest hiveminds to shut her down. He was wrong. She was fundraising for cancer.

This morning, Reddit user Beertime became suspicious of a user named mtcame07 who had repeatedly posted about how she was shaving her head to raise money for kids' cancer treatments. She had solicited donations through her personal website and PayPal account, and frequently deleted her posts. This set off Beertime's highly-tuned scam alert.

"PLEASE do not give any of your money to this woman claiming to shave her head for cancer. It's obviously a huge scam," he wrote. "Can we all please band together and call this person on their shit and make them go away." Here Beertime appealed directly to Reddit users' do-gooder inclinations. Fighting corruption is to Reddit what harassing 11-year-olds is to 4chan. One time, Redditors found the phone numbers to some obnoxious telemarketers and flooded them with calls.

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So the thread was voted up by hundreds of users until it was promoted to the top of the front page. Not a good place to be exposed as a fraud: Reddit boasts of the largest communities on the Internet, with more than a billion pageviews last month.

"Bullshit. I just reported your name and all your sites to the police for fraud," user Fabtastik wrote in the thread, including links to the FBI's Computer Crime Center and the SEC's fraud complaint site. Another user tracked down mtcame07's Facebook account, while others threatened to flood her house with pizza. But a few users urged caution: "don't go on a torch and pitchfork rage against that person on the internet. That never ends well."

In this case, Redditors were raising their pitchforks against 21-year-old St. Lawrence University senior Maya Gilsey. Tomorrow, Gilsey really is going to shave her head to raise money for Golisano Children's Hospital in Syracuse, New York, then donate her hair to Wigs for Kids. Gilsey posted about it on Reddit this morning and was shocked to come back after class to find Beertime's rant on the front page along with hundreds of angry Redditors calling for her head. Her website had been shut down after someone reported it as a fraud, and her boyfriend was getting nasty emails accusing him of being in on the scam.

"It was a little discouraging today because I'm shaving my head tomorrow," she told us over the phone. "I was getting pumped up. Now this sucks."

Gilsey explained that she had to use her personal PayPal account and website because the hospital didn't have a suitable donations system in place when she started fundraising. She posted this date-stamped picture to show Reddit users that she was a real person:

Beertime, the original poster, was basically convinced. Chastened, he updated his original rant: "There is a good chance this girl is legit... she exists and has been threatened by thousands of goons and reported to the police, FBI, and paypal at this point. She seems scared and extremely worried."

Gilsey said she was a little frightened by the fact that a local newspaper's article about her cancer fundraising scrutinized by Reddit's vigilantes contained her real address. But she says she's still shaving her head tomorrow at 4:30pm at an event on St. Lawrence's campus.

"Don't judge others too quickly," she said. "People are still out there doing good things."

In fact, all this controversy might have been good for the cause: Gilsey has raised $4,000 so far—$300 from Reddit users. If you want to donate to the Golisano Children's Hospital, you can do so through the new, official website they set up for Gilsey here. She said she'll send us some pictures of her shorn head when she's done, providing all you haters with the forensic-level evidence that is apparently the only thing that can calm the e-mob these days. Then you can try to figure out if it's photoshopped.